Caspase-3, caspase-8, and nuclear factor-kappaB expression in human cholesteatoma

Cholesteatoma is characterized by the accumulation of keratinizing epithelium resulting from the proliferation and differentiation of epithelium. Researchers are presently unraveling the role that apoptosis plays in the disease seen in cholesteatoma epithelium. Caspases play a key role in apoptosis. Caspase-8, which is activated by the induction of tumor necrosis factor-alpha, leads to activation of caspase-3, which activates apoptotic nucleases. Nuclear factor-kappaB is a transcription factor known to inhibit apoptosis induced by tumor necrosis factor-alpha. In this study, we hypothesized that expression of caspase-3, caspase-8, and nuclear factor-kappaB is uniquely connected to the proliferation, differentiation, and programmed cell death of keratinocytes during the growth and development of cholesteatoma. We obtained 41 cholesteatoma specimens for this study. The presence of these proteins in cholesteatoma was examined using immunohistochemistry and a colorimetric assay system. We also examined the patterns of apoptosis by using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining. Using the immunoperoxidase staining method, caspase-3 was found to be densely localized in the spinous and granular layers of cholesteatoma epithelium; caspase-8 was also found in the granular layer. Nuclear factor-kappaB was localized densely in the perinuclear region of the epithelium. The results obtained with immunoperoxidase staining agreed with those obtained with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining. In addition, the colorimetric assay method was used to measure the activity of caspase-3. These findings suggest that caspase-3 and caspase-8 play important roles in programmed cell death, which results in the accumulation of keratin debris during the growth of cholesteatoma. Nuclear factor-kappaB was found in cholesteatoma epithelium, but the transcription factor appeared to be inactivated.